content: /**
   * Copyright (c) 2016-present, RxJava Contributors.
   *
   * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in
   * compliance with the License. You may obtain a copy of the License at
   *
   * http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software distributed under the License is
   * distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See
   * the License for the specific language governing permissions and limitations under the License.
   */
  
  package io.reactivex.flowable.internal.operators;
  
  import java.util.concurrent.Callable;
  
  import org.reactivestreams.*;
  
  import io.reactivex.common.RxJavaCommonPlugins;
  import io.reactivex.common.exceptions.Exceptions;
  import io.reactivex.common.functions.BiFunction;
  import io.reactivex.common.internal.functions.ObjectHelper;
  import io.reactivex.flowable.ParallelFlowable;
  import io.reactivex.flowable.internal.subscribers.DeferredScalarSubscriber;
  import io.reactivex.flowable.internal.subscriptions.*;
  
  /**
   * Reduce the sequence of values in each 'rail' to a single value.
   *
   * @param <T> the input value type
   * @param <R> the result value type
   */
  public final class ParallelReduce<T, R> extends ParallelFlowable<R> {
  
      final ParallelFlowable<? extends T> source;
  
      final Callable<R> initialSupplier;
  
      final BiFunction<R, ? super T, R> reducer;
  
      public ParallelReduce(ParallelFlowable<? extends T> source, Callable<R> initialSupplier, BiFunction<R, ? super T, R> reducer) {
          this.source = source;
          this.initialSupplier = initialSupplier;
          this.reducer = reducer;
      }
  
      @Override
      public void subscribe(Subscriber<? super R>[] subscribers) {
          if (!validate(subscribers)) {
              return;
          }
  
          int n = subscribers.length;
          @SuppressWarnings("unchecked")
          Subscriber<T>[] parents = new Subscriber[n];
  
          for (int i = 0; i < n; i++) {
  
              R initialValue;
  
              try {
                  initialValue = ObjectHelper.requireNonNull(initialSupplier.call(), "The initialSupplier returned a null value");
              } catch (Throwable ex) {
                  Exceptions.throwIfFatal(ex);
                  reportError(subscribers, ex);
                  return;
              }
  
              parents[i] = new ParallelReduceSubscriber<T, R>(subscribers[i], initialValue, reducer);
          }
  
          source.subscribe(parents);
      }
  
      void reportError(Subscriber<?>[] subscribers, Throwable ex) {
          for (Subscriber<?> s : subscribers) {
              EmptySubscription.error(ex, s);
          }
      }
  
      @Override
      public int parallelism() {
          return source.parallelism();
      }
  
      static final class ParallelReduceSubscriber<T, R> extends DeferredScalarSubscriber<T, R> {
  
  
          private static final long serialVersionUID = 8200530050639449080L;
  
          final BiFunction<R, ? super T, R> reducer;
  
          R accumulator;
  
          boolean done;
  
          ParallelReduceSubscriber(Subscriber<? super R> subscriber, R initialValue, BiFunction<R, ? super T, R> reducer) {
              super(subscriber);
              this.accumulator = initialValue;
              this.reducer = reducer;
          }
  
          @Override
          public void onSubscribe(Subscription s) {
              if (SubscriptionHelper.validate(this.s, s)) {
                  this.s = s;
  
                  actual.onSubscribe(this);
  
                  s.request(Long.MAX_VALUE);
              }
          }
  
          @Override
          public void onNext(T t) {
              if (!done) {
                  R v;
  
                  try {
                      v = ObjectHelper.requireNonNull(reducer.apply(accumulator, t), "The reducer returned a null value");
                  } catch (Throwable ex) {
                      Exceptions.throwIfFatal(ex);
                      cancel();
                      onError(ex);
                      return;
                  }
  
                  accumulator = v;
              }
          }
  
          @Override
          public void onError(Throwable t) {
              if (done) {
                  RxJavaCommonPlugins.onError(t);
                  return;
              }
              done = true;
              accumulator = null;
              actual.onError(t);
          }
  
          @Override
          public void onComplete() {
              if (!done) {
                  done = true;
  
                  R a = accumulator;
                  accumulator = null;
                  complete(a);
              }
          }
  
          @Override
          public void cancel() {
              super.cancel();
              s.cancel();
          }
      }
  }
  